1. Field of the Invention
This invention relates to a grounding device for protecting electrical systems from voltage surges and for stabilizing voltage during normal operating conditions, and more particularly to a grounding cage apparatus for reducing electrical resistance, which is economical to manufacture and install. A method of providing effective grounding is also provided which utilizes the grounding cage apparatus. 2. Description of the Related. Art
Various grounding methods have been employed to protect electrical systems from voltage surges due to lightning or the like. For example, conventional lightning rods, or the use of metal water piping and metal frames of buildings are typically employed for such grounding. Devices have been developed to potentially optimize grounding. For example, U.S. Pat. No. 2,111,799 discloses a grounding device having stacked rods driven deeply into the earth. However, mechanical stresses imposed while installing this type of device may result in failure of the device when exposed to subsequent fault current values. In addition, it is typical to arbitrarily install one set of ground rods after another until the desired ohmic value is obtained, which increases both cost and installation time.
Further, conventional grounding devices are not designed to accommodate soil of varying resistances. Thus, conventional multiple stacked ground rods may lose their low ohmic value when installed too deeply or too shallowly into the earth. For example, in high resistance soils (soils with a resistivity exceeding 50,000 ohms-cm) the depth of the grounding system must be extended to extreme distances to reach soil of suitable moisture to obtain a desirable resistance value. The cost to bore holes to achieve these depths, however, have become prohibitive in certain soils.
Accordingly, it can be appreciated that a need exists to provide an improved grounding apparatus employed in a grounding method which gives a calculated ohmic reduction for a particular type of soil, without requiring increased depth penetration of the full diameter of the device. Thus, it is desirable to provide a grounding apparatus, whereby the grounding effect in various soils can be determined in advance of installation.